1. Field of the Invention
This application is related to motor speed and torque controllers for both positive and negative torques, and to motor starters, and power output controllers. This invention relates to such controllers for brush-type machines, and more particularly, to controllers for brush-type electrical machines of the type disclosed in the referenced co-pending application titled Multiple Windings Electrical Machines.
2. Background Art
Previous brush-type electrical machine controllers have used series resistance to control speed and torque and current, especially the excessive currents caused during the starting of series motors. The control of these brush-type machines is very important in considering the application of these motors. There has been a lack of a reliably-operating, efficient controller for brush-type machines. The speed and torque of a series motor energized from a constant potential supply can be controlled by inserting resistance in series with the supply line. Speed control for shunt and compound motors can be obtained by inserting resistance in series with the armature circuit only. The stator field flux of shunt motors can be varied to control the speed of these motors, although special care is required to prevent overspeeding of the motor if the shunt stator field flux becomes very weak. The speed of DC motors can be varied by varying the voltage applied to the motors; the Ward Leonard system of speed control is an example of varying the voltage applied to the DC motor. In the Ward Leonard system the adjustable output voltage from a motor-generator set is applied to the motor. Electric vehicle motor controllers use semiconductor chopper controllers as well as electromechanical switches to connect resistors and batteries in various combinations to regulate electrical power input to the motor, which thereby control the motor output torque.
Torque or force generated by a rotary or linear motor, respectively, are each a cause for, tend to cause, relative movement of the respective motor stator with respect to the respective motor armature. Torque is a cause for relative movement between armature and stator in a rotary motor, and force is a cause for relative movement between armature and stator in a linear motor.
3. Multiple Windings Electrical Motor
The motor comprises a stator and an armature, which are constrained with respect to each other by bearings means to bidirectional movement of the armature along only one axis. The stator comprises a stator magnetic yoke, stator magnetic poles, structural support means, a key means interlocking the stator magnetic yoke and the structural support means, magnetomotive force means, a brush holder means, brushes, and electrical energy coupling means. The stator magnetomotive force means are either stator windings with current flowing through them, or permanent magnets. The brush holder means positions the brushes and spring-loads them against the commutator and insulates the brushes from each other. The armature comprises a magnetic armature with teeth regularly spaced at the armature winding pitch, a commutator with conducting commutator segments, multiple open circuit armature windings per repeatable section attached to and electrically insulated from the magnetic armature and each other and with active edges of each winding spaced one stator pole pitch apart in the direction of relative movement, a mechanical energy coupling means, and a key means interlocking the magnetic armature and the mechanical energy coupling means. The armature and stator are constrained with respect to each other by bearing means which are mounted between the stator structural support means and the armature mechanical energy coupling means, so that there is an air gap separating the armature from the stator, and particularly separating the magnetic armature and the stator magnetic poles.
The armature and stator are preferred to have roughly equivalent magnetic energy, which is the magnetomotive force times the flux density times the volume, to more effectively interact with each other. The number of multiple armature windings is chosen for smoothness of operation, practicality, controllability, and convenience. It is recognized that an electrical motor of this type could be configured to have more armature windings than stator windings or that there could be no stator windings, as in a permanent-magnet field motor. The commutator has uniformly sized and spaced conducting, commutator segments which are insulated from the armature mounting and each other. It is preferred that one end of each armature winding be electrically connected to one and only one commutator segment; however, it is recognized that there could be additional commutator segments not connected to any armature winding, and that there could be more than one commutator segment electrically connected to one armature winding end. It is preferred that the number of commutator segments be equal to the number of armature winding ends, and that also equals the number of armature teeth or winding slots or winding positions; it is also preferred that the armature winding ends be connected electrically to the closest commutator segment.
A multiple windings electrical motor may be constructed of any practical number of stator pole pairs, which are also called repeatable sections; double-dashed lines in certain of the FIGS. 1 through 18, mark the boundaries of one repeatable section of the motors shown. Repeatable sections are interconnected at the stator magnetic yoke, the stator structural support means, the brush holder means, the armature mechanical energy coupling means, the magnetic armature, the commutator, and at the electrical energy coupling means.
In operation, the multiple windings electrical motor utilizes external energy to establish a magnetic field and magnetic flux which links the stator magnetic yoke, stator magnetic poles, magnetic armature, air gap, armature windings, and stator windings, when they are present. The external energy for the motor is supplied by an electrical energy source such as a unidirectional voltage source; the electrical energy source may be an alternating current source when the electrical motor is a universal type; some of the external energy may be supplied by one or more permanent magnets when such permanent magnets are used to establish the stator magnetomotive force.
The multiple windings electrical motor includes brush vacancies--two brush vacancies per repeatable section. These vacancies are used to avoid shorting between positive and negative voltages, or AC voltages, by a brush bridging two commutator segments, and to interrupt the armature current and initiate the energy disposal from an armature winding-to-be-commutated. The brush vacancies divide the brushes into two groups called first brush group means and second brush group means.
Stator windings with current flow or permanent magnets magnetically energize the stator magnetic poles. Armature windings with current flow establish armature electromagnetic poles. These stator magnetic poles and armature electromagnetic poles are positioned with respect to each other so that the total magnetic field energy of the motor will incrementally increase when the energized armature windings move incrementally with respect to the stator; this is the method of force or torque generation by both linear and rotary motors. The magnitude of the force or torque generated is proportional to the change in the motor magnetic field energy per unit relative movement. The commutation of the armature windings is designed to maintain the force or torque generating actions of the stator and armature described above, by continuously re-establishing these positional relationships, approximately, in spite of relative movement.
The energy in the interrupted armature winding can be disposed of by dissipating it or by recovering it for re-use. To dissipate the interrupted armature windings energy external to the multiple windings electrical motor, add electrical connections from the group brushes to externally located dissipating devices through half bridge circuits; the diodes of the half bridge circuits are connected to be normally back-biased and only forward-biased when the energy dissipation is being done. The various types of energy dissipating devices considered are: resistors, back-to-back zener diodes, back-to-back selenium clipper diodes and varistors. The recovery of energy from interrupted armature windings is believed to be a new concept, and one which will improve the efficiency of electrical machines.